function question(){
    var c1=document.getElementById("ques");
    var c2=document.getElementById("ans");
    c1.style.display='';
    c2.style.display='none';
}
function answer(){
    var c1=document.getElementById("ques");
    var c2=document.getElementById("ans");
    c1.style.display='none';
    c2.style.display='';
}